Ferns belong to a group of plants called featherplants or pteridophytes, along with club mosses and horsetails.
Featherplants are among the world’s most ancient plants, found as fossils in rocks 400 million years old.
Coal is made largely of fossilized featherplants of the Carboniferous Period 360 – 286 million years ago.
There are now 10,000 species of fern living in damp, shady places around the world.
Some ferns are tiny, with mossy leaves just 1 cm long.
Rare tropical tree ferns can grow up to 25m tall.
Fern leaves are called fronds. When new they are curled up like a shepherd’s crook, but they gradually uncurl over time.
Coal is made from dead plants such as ferns. Over 200 million years ago, the ferns would have become buried underground and very gradually turned to cool under the immense pressure of the Earth.
Ferns grow into new plants not from seeds but from spores in two stages.
First spores are made in sacs called sporangia. These are the brown spots on the underside of the fronds. From these spores spread out. Some settle in suitable places.
Second spores develop into a tiny heart-shaped plant called a prothallus that makes male and female cells. When bathed in rain, the male cells swim to the female cells, fertilizing them. A new root and stem then grow into a proper fern frond and the tiny prothallus dies.